script: dtc: clean generated files
script: dtc: clean generated files

Fix "make distclean" to clean up generated dtc files.

Without this patch the following files are left around:
 - dtc-lexer.lex.c
 - dtc-parser.tab.c
 - dtc-parser.tab.h

Signed-off-by: Magnus Damm <2336f5729424d0c84d319e991b3648cafa2c3c5b@opensource.se>
Reviewed-by: Simon Horman <a105fd58f578dea0be108941d4c59d15396e1855@verge.net.au>
Signed-off-by: Grant Likely <9069e6f5a2b566e2674a0ba1e2bf39c12c195fad@secretlab.ca>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas